The primary purpose for catalytic cracking of hydrocarbons is the production of gasoline. Although the desired product distribution from this process may change, e.g., because of variations in seasonal demand, it is important to produce gasoline having the highest octane number, to minimize processing downstream from the cracking unit.
Methods by which the octane number of gasoline range hydrocarbons can be raised include increasing the branching of paraffins, dehydrogenating paraffins to mono-olefins, and converting both paraffins and olefins to aromatic hydrocarbons. This invention discloses a process by which the octane rating is increased on gasoline made by catalytic cracking over a catalyst that is contaminated with metals. The contamination results from processing feedstocks containing naturally occurring compounds of vanadium, iron, and nickel; adventitious metals from process equipment can also contribute to the catalyst contamination.